1. Technical Field
The present invention is related to a method for operating non-volatile memory devices, and more particularly, to a method for read disturbance management in non-volatile memory devices.
2. Description of the Conventional Art
Semiconductor memory devices are generally divided into two groups: volatile memory devices and non-volatile memory devices. Volatile memory devices include Dynamic Random Access Memory (DRAM) devices and Synchronous Random Access Memory (SRAM) devices. Non-volatile memory devices include Electrically Erasable Programmable Read Only Memory (EEPROM) devices, Ferroelectric Random Access Memory (FRAM) devices, Phase-change Random Access Memory (PRAM) devices, Magnetic Random Access Memory (MRAM) devices, and flash memory devices, etc. When power supply is cut off, volatile memory devices lose the data stored therein, while non-volatile memory devices can retain the data stored therein. Particularly, since flash memory devices are characterized in high programming speed, low power consumption and large-capacity data storage, they are widely used as non-volatile memory for computing devices such as desktop and laptop computers, personal digital assistants (PDAs), digital cameras, tablet computers, smartphones, and the like.
Flash memory devices, such as NOR-type flash memory devices with excellent random access time characteristics or NAND-type flash memory devices with high integration degree, may adopt different cell structures in which electric charges may be placed on or removed from a flash memory cell to configure the cell into a specific memory state. For example, a single level cell (SLC) may be configured to two single-bit binary states (i.e., 0 or 1). Similarly, a multi-level cell (MLC) may be programmed to two-bit states (i.e., 00, 01, 10, or 11), three-bit states, and so on.
As data is being read from a flash memory device, a phenomenon known as “read disturbance” can occur to adjacent memory cells. Read disturbance is caused when a page in the flash memory device is read numerous times and adjacent memory cells are affected by electron migration to the point that the data stored in the adjacent cells is changed. The occurrence of read disturbance may impact data accuracy of SLC/MLC flash memory devices.
Therefore, there is a need for a method of improving read disturbance in non-volatile memory devices.